Inflow segment for a turbomachine

ABSTRACT

A turbomachine is provided having an inflow segment which carries an inflow segment vane and bores, a partial mass flow arriving through these bores at a relief space and leading to a cooling system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2013/064429 filed Jul. 9, 2013, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP12176161 filed Jul. 12, 2012. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a turbomachine, having a rotor which is mounted rotatably about an axis of rotation, rotor blades which are arranged on the rotor, a casing which is arranged about the rotor, guide vanes which are arranged on the casing, a flow duct which is formed between the rotor and the casing, a supply line which is arranged in the casing and is formed for supplying steam, an inflow segment which is arranged in the casing, inflow segment guide vanes which are arranged in the inflow segment.

BACKGROUND OF INVENTION

Turbomachines, such as steam turbines, are for example used for the supply of power. Such turbomachines essentially comprise a rotatably mounted rotor and a casing arranged around the rotatably mounted rotor. In general, the casing is split into an inner casing and an outer casing arranged around the inner casing. The rotors of turbomachines formed in this manner comprise rotor blades which are arranged between guide vanes arranged on the inner casing and which form a flow duct through which flows a flow medium. In one embodiment of the turbomachine, formed as a steam turbine, steam is the flow medium.

The flow medium flowing into a turbomachine is at relatively high temperatures. Thus, in steam turbines, as an embodiment of a turbomachine, the steam is heated such that the steam can be at temperatures above 600° C. Such high temperatures lead to high thermal loads on the turbomachine. The components of the turbomachine which are subjected to particularly high thermal loading are those which are arranged in the inflow region of the flow medium. Furthermore, the rotor is also subjected to particularly high thermal loading at the point at which the flow medium flows into the turbomachine. The choice of materials must be appropriate in order for the turbomachine to be operable.

However, the limits of use of a rotor are limited by this, since the thermal load is permissible and possible only up to a limit value. For example, the decisive strength parameters of the materials used yield disproportionately at excessive temperatures. From the temperature of the rotor material, it is possible to derive for example the maximum permissible shaft diameter, relative to the load on the shaft interior, or also the maximum permissible centrifugal forces in that region of rotors which is close to the rim, which in particular at 60 Hz applications can lead to limitation. This is remedied by lowering the temperature, which can be achieved by cooling the surface or by cooling the shaft interior, which achieves either a broadening of the mechanical limits of use of the rotor for a given material or, in other cases, makes it possible to avoid a change to higher-value and more expensive materials.

Current turbomachines have an inflow segment which is arranged in the supply duct of the turbomachine. This inflow segment has a guide vane ring. The fresh steam flowing into the turbomachine comes into contact first with the guide vanes of this inflow segment. In general, this inflow segment is arranged on the inner casing. One physical effect which can be achieved with the inflow segment is that the fresh steam has increased swirl and thus leads to temperature-lowering effects of the inflow relief slot. This achieves a moderate cooling which reduces the thermal load on the first turbine blade roots and on the shaft interior. Such inflow segments are also termed diagonal stages.

SUMMARY OF INVENTION

The invention has set itself an object of proposing an improved turbomachine.

This is achieved by a turbomachine according to the independent claim.

An essential feature of this turbomachine is that bores are created which are arranged in the inflow segment and which establish a fluidic connection between the supply line and a relief space which is arranged between the inflow segment and the rotor.

According to aspects of the invention, it is thus proposed to further lower the temperature at the shaft surface by arranging bores which are executed as tangential bores. This imparts a predefined circumferential velocity to the flow of the flow medium beneath the inflow segment. This results in the desired cooling effect at the shaft surface. Wetting the region of the shaft surface in the relief slot with temperatures below the fresh steam temperature also results in a temperature drop in the region of the shaft axis beneath the first rotor blade anchor.

Advantageous developments are proposed in the subclaims.

Thus, in a first advantageous development, the bores are formed such that part of the supply steam is fed through the bores and part of the supply steam is fed through the inflow segment guide vanes.

In a further advantageous development, the inflow segment has a hub-side ring segment in which are formed the bores.

Advantageously, the bores are arranged upstream of the inflow segment guide vanes, as seen in the flow direction of the supply steam. It is thus possible for part of the steam to be diverted immediately before it flows through the inflow ring. This makes improved cooling possible.

Advantageously, the bores are inclined, with respect to a radial direction through the axis of rotation, by an angle α of between 40° and 80°. It is thereby possible to achieve optimum cooling effects since the swirl of the steam flowing in beneath the inflow segment is essential for the most effective possible cooling.

In one advantageous development, six bores are formed, wherein the number is influenced by the respective shape, thermodynamics and magnitude of the desired cooling effect.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail with reference to an exemplary embodiment and with reference to the schematized drawings, in which:

FIG. 1 is a schematic section view through part of a turbomachine;

FIG. 2 is a partial perspective view of an inflow ring;

FIG. 3 is a section view through the inflow ring.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a detail of a turbomachine. The turbomachine shown in FIG. 1 is formed as a steam turbine 1. The steam turbine 1 has a rotor 3 which is mounted rotatably about an axis of rotation 2. The rotor 3 has various diameters. Rotor blades 5 are arranged on a rotor surface 4. For the sake of clarity, only one rotor blade 5 is shown. The rotor blade 5 has a rotor blade root 6 which is arranged in a corresponding rotor slot 7. The rotor material immediately adjacent to the rotor blade root 6 is also termed the rotor blade anchor.

Around the rotor 3, there is arranged an inner casing 8 which is essentially, and depending on the construction, formed from an upper inner casing part and a lower inner casing part, in the case of a horizontal parting joint, or in corresponding fashion is formed from a left inner casing part and a right inner casing part, in the case of a vertical parting joint. An outer casing 9 is arranged around the inner casing 8. A sealing element 10 is arranged between the inner casing 8 and the outer casing 9.

The inner casing 8 is formed such that a supply line 11 is formed by a steam supply, not shown in more detail. This supply line 11 supplies fresh steam which can be at temperatures of up to 650° C. or more. The inner casing 8 also carries guide vanes 12 which are arranged in corresponding inner casing slots 14 via guide vane roots 13.

For the sake of clarity, only one guide vane 12 is shown. A flow duct 15, which is formed by the guide vanes 12 and the rotor blades 5, is created between the inner casing 8 and the rotor 3. The rotor 3 is formed with a thrust-equalizing piston 16 which has a substantially larger diameter. A shaft seal 18 is formed between the surface 17 of the thrust-equalizing piston 16 and the inner casing 8. Upstream of the thrust-equalizing piston 16, as seen in the rotation direction, the rotor 2 has a smaller diameter, wherein a second shaft seal 19 is arranged in this section.

The supply line 11 is provided to supply steam and is formed accordingly. The inner casing 8 has, in this region, a projection 20 against which an inflow segment 21 is arranged. The inflow segment 21 is substantially formed as a ring and is installed in the inner casing 8. At the outer diameter of the inflow segment 21, the inflow segment 21 is fitted into a slot 22. The inflow segment 21 has a hub-side ring segment 23 which is connected to the inner casing 8 via a second sealing element 24. To that end, the hub-side ring segment 23 has a sealing slot 25 into which the second sealing element 24 is fitted. Moreover, the inner casing 8 also has a slot 26 in which the other end of the second sealing element 24 is arranged. The inflow segment 21 has inflow segment guide vanes 27 which are formed in one piece with the inflow segment 21. The rotor 3 is formed with a relief slot 28 which is essentially characterized by a smaller diameter and has a certain radial separation from the inflow segment 21 in order to form the relief space 30. In the installed state, the inflow segment 21 ensures, by means of the sealing elements and installation situation, a technical steam-tight separation of the supply duct 11 from the relief space 30. Bores 29 are arranged in the hub-side ring segment 23 in the inflow segment 21. These bores 29 establish a fluidic connection between the supply line 11 and a relief space 30 which is formed between the inflow segment 21 and the rotor 3.

In operation, a mass flow rate (M_(ges)) flows in the supply line 11. This mass flow rate splits into a smaller mass flow rate (M₁), which passes through the bores 29 and enters the relief space 30, and a larger mass flow rate (M₂), which flows through the inflow segment guide vanes 27 and then passes through the flow duct 15. M_(ges)=M₁+M₂, where M₁<<M₂. Furthermore, the mass flow rate M₁, which passes through the bores 29, splits into a mass flow rate M₁₁, which enters a thrust-equalizing piston antechamber 31 via the second shaft seal 19. Another part of the mass flow rate M₁, as second mass flow rate M₁₂, passes along the hub-side ring segment 23 and into the flow duct 15.

The mass flow rate _(M) ₁₁+M₁₂ is at a lower temperature than M_(ges) and thus contributes to cooling the rotor surface in the relief slot 28.

The bores 29 are arranged upstream of the inflow segment guide vanes 27, as seen in the flow direction 32 of the supply steam.

FIG. 2 shows a partial view of the inflow segment 21. The perspective shown in FIG. 2 shows a view outwards from the axis of rotation 2, in the radial direction. The perspective shown shows multiple inflow segment guide vanes 27. The hub-side ring segment 23 is essentially triangular in shape and has the slot 25 for receiving the sealing element 24. FIG. 2 shows a perspective of the inflow element 21 showing an inner surface 33 of the hub-side ring segment 23. The outlet 34 from the bores 29 is formed on this inner surface 33.

FIG. 3 shows a section view through the inflow segment 21. For the sake of clarity, only one inflow segment guide vane is provided with the reference sign 27. In the chosen exemplary embodiment, six bores 29 are created, which are formed in a tangential direction to the relief space 30, at the angle α. The direction of rotation of the rotor 3 is counterclockwise. The angle α is labeled by way of example on the bore 29 at the twelve o′clock position. A reference line 35 is shown, proceeding in the radial direction from the axis of rotation 2. A bore 29 is created at an angle α of between 40° and 80°. The mass flow rate M₁ flows through this bore 29. The imparted swirl changes the velocity of the steam, whereby the static temperature of the steam is lowered relative to the rotating system, which then leads to a cooling of the surface of the rotor 3 with respect to the temperature of the mass flow rate M_(ges). 

1-8. (canceled)
 9. A turbomachine, comprising a rotor mounted rotatably about an axis of rotation, with rotor blades arranged on the rotor, a casing arranged about the rotor, with guide vanes attached inside the casing, a flow duct formed between the rotor and the casing, a supply line arranged in the casing and formed for supplying steam, an inflow segment arranged in the casing, inflow segment guide vanes arranged in the inflow segment, and bores arranged in the inflow segment which establish a fluidic connection between the supply line and a relief space arranged between the inflow segment and the rotor, wherein the bores are inclined, with respect to a radial direction through the axis of rotation, by an angle α of between 40° and 80°.
 10. The turbomachine as claimed in claim 9, wherein the bores are formed such that part of the supply steam is fed through the bores and part of the supply steam is fed through the inflow segment guide vanes.
 11. The turbomachine as claimed in claim 9, wherein the inflow segment has a hub-side ring segment in which are formed the bores.
 12. The turbomachine as claimed in claim 9, wherein the bores are arranged upstream of the inflow segment guide vanes, as seen from the flow direction of the supply steam.
 13. The turbomachine as claimed in claim 9, wherein six bores are formed.
 14. The turbomachine as claimed in claim 9, wherein the casing is formed as an inner casing and an outer casing is arranged around the inner casing.
 15. The turbomachine as claimed in claim 9, wherein the turbomachine is formed as a steam turbine. 